The present invention relates to energy delivery devices, and more particularly, to hierarchically arranged energy delivery systems that facilitate scalability and fault tolerance.
Many examples exist of parallel redundant systems, such as batteries, electric power supplies, computer hard drives, microprocessors, and communication links. Failover methods exist whereby failures of one or more components of the parallel redundant system does not result in overall system down time.
At present, state-of-the-art Energy Delivery Systems (EDSs) are often connected in parallel to provide such redundancy. Power supplies, batteries and generators are all well-known examples of such systems.
FIG. 1A illustrates a prior art battery management system (BMS) 10 for which a central battery management component 12 is connected to every battery cell or series element 14 in the string 16.
FIG. 1B illustrates a prior art BMS 20 for which the central battery management component 22 receives information from individual cell monitoring components 28 coupled to each cell or series element 24. In the architecture of FIG. 1B, data associated with each battery cell or series element 24 passes down-stream through cell monitoring components 28 before reaching the central battery management component 22.
A disadvantage of these redundant prior art systems is that their scalability in multiple directions is limited. Prior art BMS's are usually custom designed for a specific configuration of batteries, by number of cells when connected in series, and by size of battery when connected in parallel. In order to expand the size of the battery pack, new circuit cards must be designed with additional connections and sensing circuits.
Central battery management systems 10 (as shown in FIG. 1A) that interface to every cell or series element 14 suffer the disadvantage of having many wires connected throughout the battery pack. The long wires carrying voltage and temperature information about each of the battery elements are subject to significant electromagnetic interference, which degrades the signal integrity and lowers the measurement accuracy of the BMS 10. In addition, the wires may have high voltages relative to other wires connecting to the BMS circuit card that hosts the central battery management component 12. This requires careful PCB layout and connector design to prevent high voltage interference to other circuit functions and hazard free operation.
Series configured cell-monitoring solutions (as shown in FIG. 1B) suffer limitations of not being able to scale too many cells 24 in series due to the inability of the cell monitor devices 28 to pass through information from a large number of series connected cells. Typical pass-through methods cause each cell monitor 28 to accept information from downstream monitors 28, buffer the information, append their own information, and then pass the packet upstream toward the next monitor closer to the central battery management component 22. As it travels from monitor to monitor, the packet increases in size. At some point, the packet may become too large to fit into the memory buffer of any one of the series monitors. Consequently, this scheme is generally limited to about 25 cells. In any case, as the series string become larger, the time it takes for information to ripple from the last monitor in the string to the BMS 22 becomes untenable for suitably responsive system operation.
Further, when one of the series elements fails, it generally cannot pass information from other modules in the series upstream to the BMS 22.
Finally, there is incrementally more cost to having an intelligent measuring and communicating device attached to each series element in the battery string. Usually, such systems can be scaled in either the parallel direction or the series direction, but not both. Meaning, such systems can add more parallel elements or add more series elements either in the design phase or in the assembly phase, but not both.
Prior art systems also suffer limitations of not being able to scale a large number of cells in series due to the inability for system controllers to communicate across high voltage boundaries.
Conventional battery module designs are usually large scale, custom packs designed for specific applications. More compact, scalable, and multi-configurable battery pack solution from one common base package is needed.